Radio signaling apparatus



Feb. 5, 1929. 1,701,336

E. L. POWELL RADIO SIGNALING APPARATUS Filed July 10, 1925 gwmwloc E04)! .5. f d/re]! Patented Feb. 5, 1929.

UNITED STATES PATENT OFFICE.

EDWIN L. POWELL, OF WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOB TO WIRED RADIO, INC., 01 NEW YORK, N. Y., A CORPORATION OF DELAWARE.

RADIO SIGNALING APPARATUS.

Application filed July 10, 1925. Serial 1T0. 42,771.

My invention relates broadly to radio receiving apparatus and particularly to radio receiving apparatus using auxiliary local oscillating circuits to heterodyne with incoming radio signals, well-known'in the art as heterodyning or superheterodyning.

The object of my invention is to provide a circuit to impress the heterodyning oscillations onto the received signals and at the same time to eliminate any detuning of the auxiliary oscillating circuit while tuning the incoming receiving circuits.

Further objects of my invention will appear more fully hereinafter.

My invention consists substantially in the construction, combination, and arrangement of parts and circuit arrangements associated therewith, all as will be more fully hereinafter set forth as shown by the accompanying drawing and pointed out in the appended claims.

Reference is to be had to the accompanying drawing forming a part of this specification in which the figure represents a schematic diagram of my invention.

1, 2 and 3 represent a primary circuit of a radio receiver, 4 and 5 the tuned secondary circuit inductively connected thereto, 6 a stopping condenser, 7 a vacuum tube, and 8 a grid leak, all connected as shown and as is well-known in the art. Vacuum tube 9 has a tuned grid circuit made up of inductance 10 and condenser 11. Coupling of the plate circuit to the grid circuit is by means of coil 12. Coil 13 is a chokecoil in the plate battery circuit to prevent the oscillations set up by tube 9 and associated circuits from passing through the plate battery. The feedback circuit of the local oscillation tube,

which carries only the radio frequency component of the direct current in the plate circuit of tube 9, is completed to the filament from the low potential end of the tickler coil 12 through parallel paths, one leg of which is through condenser 14 and the other leg is through condenser 15 and grid leak 8. The vacuum tube 9 and associated circuits make up a generator of local oscillations to heterodyne with the received radio signals.

The principle of superheterodyne reception incorporates a first detector circuit tuned to the frequency itis desired to receive and a heterodyne oscillation circuit coupled thereto tuned to a higher or a lower frequency, the plate circuit of the first detector being resonant to the difference of the frequencies or the beat frequency thus formed. This beat frequency is then amplified to the desired degree by means of a multi-stage intermediate frequency amplitier and again rectified by a second detector. For the reception of continuous wave signals a second local oscillating circuit is required for the production of audible beats.

Heretofore the adjustment of the superheterodyne receiving apparatus for receptlon of continuous waves has been quite difficult, due to the fact that the first detector and heterodyning circuits were of necessity inductively coupled together and a. reaction caused by the tuning of the first detector circuit dragged or. varied the frequency of the heterodyne oscillator, resulting in a variation of the audible beats heard in the phones. This variation of the heterodyne frequency although not generally noticeable in the reception of damped or modulated signals, was so pronounced in the reception of continuous waves of supershort wave lengths, say 70 meters, that operation became impracticable and a new method of coupling and superposition was necessary to overcome this inherent fault in the superheterodyne system.

The novel featureof'my invention is in the method of coupling the heterodyne oscillations to the incoming signals in the grid filament inputcircuit of the first detector tube.

'Instead of inductively coupling these oscillations to coil 2 or coil 4, as heretofore. the local oscillations are conducted direct to the grid of the first detector tube through one leg of the tickler feed back circuits previously mentioned, and thence along grid leak 8 to the filament; the desired local variations on the grid-filament input to the first detector tube 7 being made effective by the drop of potential across the grid leak 8. Complete elimination of reaction between the first detector and heterodyne oscillator tuned circuits is secured by reducing the usual resistance of grid leak 8 to a low comparative value, and employing comparatively high impedance values for the" stopping condenser 6 and cou ling condenser 15. The optimum values 0 these three units will be determined by the frequency bandit is desired to cover, but for best operation their ratios, one to another, will remain praetically constant for .all frequencies. The capacity of the coupling condenser 15, being once established for a given frequency band, the pro ortion of the total energy in the tickler circuit of the heterodyne tube required to be impressed on the first detector tube for optimum reception can be secured by a proper selection of the capacity of the condenser 14. Thus for a range of wave lengths of 70 to 300 meters, condenser 14 should be approximately .001 microfarad; condenser 15, 25 micro-micro-farads; grid leak 8, approximately one mcgohm; and condenser 6, approximately 25' micromicro-farads. The value of the parts of all circuits is subject to variation to meet different conditions and is given here only to allow one familiar with the art to set up the required apparatus to determine the increased efficiency of this circuit arrangement.

The plate circuit of tube 7 is the usual superheterodyne arrangement of the first detector tube which by the proper selection of values of condenser 20 and inductance 21 is made to be resonant to the beat frequency formed by the incoming radio signals and the local oscillations generated in tube 9 and associated circuits.

The beat frequency currents are conducted to an intermediate radio frequency amplifier through contacts 18, the transfer of energy being accomplished by the tuned circuit made up of inductance l6 and condenser 17.

It will be understood that the above description and accompanying drawing comprehend only the general and preferred embodiment of my invention and that various minor changes in detail, construction, pro portion and arrangement of parts may be made within the scope of the appended claims and Without sacrificing any of the advantages of my invention.

Having described my invntion what I claim is z 1. In a signal receiving system a high fremousse quency energ collectin circuit, an electron tube detector aving ri filament and plate electrodes, input an' output circuits inter:

connecting said electrodes with the input circuit thereof connected with said high frequency energy collectin circuit, an. electron tube oscillator having grid, filament and plate electrodes, input and output circuits intercircuit of said electron tube detector for impressing high frequency oscillationsthereon while stabilizing theoperation of said oscillator.

2. In a signal receiving system 'a hi h frequency energy collecting circuit, an e ectron tube detector having input and output cir-' cuits with the input circuit thereof connected with said high frequency energy collecting circuit, an electron tube oscillator comprising input and output circuits coupled one to the other, a common cathode circuit for each of said electron tubes, a common plate supply circuit for each of said tubes, a pair of independent condensers, a connection extending from said output circuit to a terminal common to said pair of condensers, the opposite sides of said'condensers being connected to opposite sides of the input circuit of said electron tube detector,whereby oscillations generated and sustained by said last mentioned electron tube circuits may be impressed on the circuits of said electron tube detector at a frequency independent of the tuning of the input circuit of said electron tube detector.

EDWIN L. POWELL. 

